Why so much lag?

[Pstl_Pete]

Excuse my ignorance on this but I'm a bit perplexed as to why our cars suffer from so much turbo lag? Is the turbo inefficient? Or is it something else? I would think a 3.3L engine should have plenty of flow to spool a turbo really quick.

For those of you that have been able to improve spool up over stock, I'd love to hear what you did.

[Noah930]

The motor might displace 3.3 liters, but it's a low compression 3.3 liters at that.

Plus remember that this was the 3rd production turbocharged car on the market, so turbocharging was at its infancy when this motor was designed. So yes, the turbos are relatively inefficient compared to more modern designs.

[quattrorunner]

There are options. Ask rarelyl8. He's got some good turbos.

[GJF]

For the motor more compression, newer cam profile, more efficient turbo. The intake system, and fuel/ spark management. All these things done to a 930 would make massive leaps in performance. Most tend to want double or more than the factory HP. But if one were to simply shoot for 350 HP and bump up the compression with a more efficient turbo, lag would be almost nonexistant.

[1986 930]

Upgraded to B&B Headers and Exhaust + K-27HFS Turbo and it changed the whole character of the way the engine makes power. There is still some lag, but not much. I plan to add a long neck intoercooler next to help take the remaining Lag out..

[mark houghton]

Turbo lag is all about how fast the turbo recovers after the BOV dumps (or recirculates) the boosted air. The best thing you can do to minimize the lag is get rid of the stock 3LDZ and replace it with a K27 variety...either 7600 (for more top end boost) or 7200 (for earlier onset). Either will show a reduced lag. But, the larger impact is getting rid of any exhaust restrictions. That means at the very least ditching the catalytic converter, going with a through-flowing muffler (or no muffler at all....can you say Zork?), and topping it off with a set of headers. The less restriction, the better for spooling up the turbo.
You can shop around and add upgrades such as these piece-meal (as I did) or just go to a known and proven source of custom made quality parts for the entire package. See Brian @ RarelyL8.

[oilonly]

My sig below pretty much eliminated any lag on my car.

[totle]

As the the guys here have stated.
New turbo and free flow exhaust will give much improvement over stock 3LDZ turbo

This recording was done on my 78 930 after I rebuilt the stock engine.
As you see, full boost at 2300 rpm
My mods: Removed emission stuff, updated to SC cams with 1,65mm timing, new K27-7200 turbo, ported intake ports to 35mm, new headers and RarlyL8 dual out free floating muffler.

[Tippy]

Totle, wow! That's impressive spooling.

[Pstl_Pete]

Thanks for all the info gents. I've already got a K27-7200 but I still feel its got too much lag for me. With the ideas you all mention, I will definitely start replacing some of the stock parts like the exhaust headers. My concern is with tuning, I'm used to using modern EMS's so I'll have to do some reading and ensure that when I change parts out the engine is still getting proper amounts of fuel and timing.

Another quick question, has anyone used ball bearing turbos with good success?

[Tippy]

Search GT35R. A handful have used BB turbos.

[spence88mph]

Free Flowing exhaust alone reduces lag by about 1000rpm, we were shocked at the difference a rarelyL8 did to my friends 930, 4 bolts and about an hours work tops. Then switch out your turbo and possibly cams when you want to further reduce lag, I bet you'll be pretty chuffed for a while with just a muffler. Hit Brian up (rarelyL8), he's a dude.

[vas930]

Pete, you will always have some lag with these cars.
Plenty you can do to make it better, as the other guys have said.
Best thing to do is just keep the revs up.
Drive it this way for some time and you get used to it.
When driving it hard or on track, you learn to be on the gas when braking.
It takes some doing, but its all about timing the boost when you hit the apex.
Its great fun when you master this style.
And bloody quick.

Good luck.

[carreraseacat]

wow, full boost at 2,300rpm is impressive indeed!

i get full boost on my 3.0 at about 3,100rpm with the below mods.

[proffighter]

Originally Posted by totle

As the the guys here have stated.
New turbo and free flow exhaust will give much improvement over stock 3LDZ turbo

This recording was done on my 78 930 after I rebuilt the stock engine.
As you see, full boost at 2300 rpm
My mods: Removed emission stuff, updated to SC cams with 1,65mm timing, new K27-7200 turbo, ported intake ports to 35mm, new headers and RarlyL8 dual out free floating muffler.

Trond, very nice boost curve! 1.65mm timming is way away from SC timing. How do you get that value? Recommendation, testing,...?

I have 964 cams too, set to 1.26mm (stock value for 964 cams), but boost of 1bar is reached at about 3100rpm.

Do you think that early boost is mostly due the timing setting, or maybe caused by the stock exhaust ports, or what...?

I see you changed your setup since. Do you still have that early full boost (1bar?) with that new setup?